Final answer:
Muscle contraction at the NMJ involves the neurotransmitter acetylcholine binding to receptors on the sarcolemma, causing depolarization and initiating an action potential that leads to muscle contraction with the help of calcium ions.
Step-by-step explanation:
Muscle contraction at the Neuromuscular junction (NMJ) involves a series of intricate steps:
- Acetylcholine (ACh) is a neurotransmitter released by motor neurons that triggers muscle fiber depolarization at the NMJ.
- Acetylcholine receptors are proteins on the muscle fiber sarcolemma that bind to ACh, leading to the opening of ion channels.
- The synaptic cleft is the space between the neuron and the muscle fiber where ACh diffuses.
- The synaptic terminal is the end of the motor neuron's axon where ACh is released.
- Sarcolemma is the muscle cell membrane that becomes depolarized during muscle contraction.
- T-tubules are extensions of the sarcolemma that conduct the action potential into the muscle fiber.
- An action potential is an electrical signal that travels along the sarcolemma and triggers muscle contraction.
- Acetylcholine esterase is an enzyme that breaks down ACh, terminating the signal to the muscle fiber.
- The term neurotransmitter refers to chemical messengers like ACh that transmit signals across synapses.
- Motor end plate is the part of the sarcolemma with many ACh receptors where the motor neuron connects.
- Calcium ions are released within the muscle fiber to initiate the interaction between actin and myosin, leading to muscle contraction.